Switch



Jun 195 3 R. c. INGWERSEN 2,642,510

SWITCH Filed June 6, 1949 l5: Iii? jg! u R/EHA RD E JNE WEHEE/v ATTORNEYS Patented June 16, 1953 SWITCH Richard C. Ingwersen, Jackson, Mich., assignor to Mechanical Products, Inc., Jackson, Mich., a

corporation of Michigan Application June 6, 1949, Serial No. 97,356

4 Claims.

This invention relates to electrical switches and more particularly to electrical switches having overload protection as disclosed in Patent No. 2,485,736 dated October 25, 1949.

According to the overload protected electrical switch specifically disclosed in the said prior patent, a thermal latch is provided which involves a pair of bimetallic latching contacts adapted to have releasable latching engagement with shoulders on opposite sides of an insulated mounting block for a push-pull manually actuatable switch button, the block serving also for the resilient mounting thereon of a pair of flexible contact arms carrying the movable contacts of the switch assembly.

An object of the invention is to provide a switch assembly according to the said prior patent having a modified and improved construction of the thermal latch according to which the latter is required to have latching engagement on one side only of the aforesaid mounting block, whereby a uniform latching characteristic is obtainable as compared with the employment of the double sided latching arrangement of the prior patent.

Another object of the invention is to adapt the overload protected electrical switch construction of the prior patent for operation at appreciably low current values, or alternatively for the adoption of the switch for operation at appreciably high current values.

Yet another object of the invention is to provide an overload protected switch which can be easily-manufactured from standardized parts yet be readily adapted for use with an optional variety of current ratings.

Other objects of the invention are to provide an overload protected electrical switch according to the prior patent with novel and improved latching mechanism and to incorporate in the switch an electrical shunt for use when the switch is required to operate with the use of much higher currents than that for which the original switch was intended.

Another object or" the invention is to provide an overload protected switch according to the prior patent having a novel and improved construction and mounting of the terminal strips, which obviates distortion of the latter due to applied mechanical loads and such as might otherwise affect the fixed electrical contacts associated with these terminal strips.

The above and other objects of the invention will appear clear from a consideration of the foregoing detailed description with reference to the accompanying drawing and from a consideration of the appended claims.

In the accompanying drawing:

Fig. I is an elevational view of an overload protected electrical switch in accordance with the invention with the switch shown in the closed position and incorporating a single sided latching arrangement for the electrical conductor latching plate,

Fig. II is a fragmentary detail view showing the construction of the switch casing to form a mounting for the modified terminal strips,

Fig. III is an end elevational view of one construction of the switch assembly carrying the movable contacts and the associated push-pull button and latching action, the latter being shown in operation and corresponding to a closed position of the switch mechanism,

Fig. IV is a perspective view of Fig. III,

Fig. V is a plan View of Fig. III with an electrical shunt strip shown dotted in position and optionally employed, depending upon whether the switch is required to operate for lower or higher current ratings,

Fig. VI is a view similar to Fig. III, but of a modified thermal latch assembly and associated push-pull button, and

Fig. VII is a side elevational view of Fig. VI looking upon the lefthand side of that figure.

Referring to the drawings, the general construction, arrangement and operation of the switch is the same as described and disclosed in the prior Patent No. 2,485,736 and differs therefrom in respect of certain details of construction and arrangement, which however have been found to possess important advantages in actual practice and constitute important improvements upon the specific construction disclosed in the prior patent.

As in the prior patent the switch is constituted by a two-part casing construction of insulating material, one part of which is indicated at l 0 and is shown as having the fixed electrical contacts [2 mounted therein for operative association with a pair of movable contacts !4 carried upon flexible arms I6 mounted upon the end portions l8 of a pair of generally U-shape metal strips, indicated generally at 2! and piloted upon opposite sides of a block 22 of insulating material with the interposition of coil springs 24 connected between the flexible arms 46 and ear portions 26 integral with an insulator block 28 fixedly mounted in a recess 30 in the casing la).

In Figures III to V the end portions I8 are integral with the U-shape strips 20 on opposite sides of the block 22 whereas in Figures VI and VII only one end portion i 8 and integral U-shape strip 20 is provided, the opposite side of the block 22 having an associated pair of finger strips 32 bridged by an insulator strip 34 which renders these finger strips inactive electrically.

In both forms of the invention the construction and arrangement is such that a latching action takes place only on one side of the block 22 and this with respect to a ledge 36 defined by a metal plate 38 of a material, such as Phosphor-bronze, which is thermally inactive or substantially so.

Thus in Figures III to V only the strip 20 on the right hand side has latching engagement, the strip 29 on the left hand side being formed to extend down the side of the block 22 and against the edge of the bearing plate 38 when the opposite strip 20 is held latched against the surface of this plate. In this form of the invention both strips 29 are electrically conducting.

In Figures VI and VII, on the other hand, the fingers 32 extend down the side of the block 22 when the strip 2!] is held latched and since these fingers are insulated from each other by the insulator strip 34 and the bearing plate 38 is cut short of the block 28 adjacent the fingers 32 and as indicated at ll? only the strip 20 is eflectively electrically conductive.

The alternative constructions and arrangements thus described give the possibility of different current ratings, with an efiective increase or decrease in the electrical resistance as will be appreciated by those skilled in the art.

A further current rating is readily and conveniently made possible of adoption with the use of the same switch parts as thus described, simply by the addition of a conductor strip 42 in the form of a shunt connected with the contacts Hi to extend across one surface of the contact arms it. The application of this shunt strip to the switch assembly enables higher currents to be accommodated for whether or not the thermal latch construction is adapted for latching on one side, as provided for by the present development, or is adapted for latching on both sides, as in the case of the prior patent.

The assembling of the duplicate bimetallic strips 20 or the single bimetallic strip and associated non-conducting strip assembly 32 on the insulated block 22, together with the associated movable contact arms i6, is such that, as with the construction disclosed in the prior patent, it is possible to engage or disengage the contacts l4 by manual operation of the push button 4! and for the overload protection to be overriden, when desired, simply by holding the switch closed through pressure applied to the push button.

As is clearly shown in Fig. I, the terminal strips are bent into substantially angular form and have one limb 44 thereof embedded in a cross slot 46 formed in the opposed casing sections, whereas the other limb 35 of each terminal strip is held sandwiched in a correspondingly shaped composite slot 49 in the respective casing sections, the arrangement affording a secure an- 4 chorage for the angular terminal strips which prevents the latter from being displaced in operation, and hence affecting the location of the contacts.

The presence of the bearing plate 38 for active cooperation with the thermal latching strips 20 is advantageous since it affords a metal to metal bearing surface and by making the bearing plate of Phosphor-bronze, or other non-ferrous metal, a desirable bearing surface is presented which avoids wear upon the latching strips and thereby maintains the desired make and break timing factor within very close and precise limits in the continued use and operation of the switch. Such might not be possible in the absence of the bearingplate, due to the attendant wearing of the material of the insulator block 22 if this were relied upon for the direct bearing contact of the latching strips.

The single side latching action made possible with the modified switch construction of the present invention possesses the advantage that since the latching action is required to take place only on one side it is possible to maintain a uniform latching characteristic such as could not be relied upon as existing in the case where the construction is adapted for the latching operation to take place along each side of the block 22.

The invention provides a highly eflicient pushpull manual switch with overload protection which can be adapted to the handling of excessive high overloads without damage to the switch mechanism and which provides for the obtaining in a ready manner and with the use of standardized parts of a variety of different current ratings, depending upon the particular requirements and circumstances.

Having thus described my invention, what I consider to be novel and wish to cover by Letters Patent is as follows:

1. In an electric switch having current overload protection, a casing including fixed guide structure and fixed guide structure including an abutment ledge on one side and defining a guide surface on its opposite side, fixed contacts in aid casing, a support structure movably mounted on said guide structure, said support structure carrying movable contacts in opposed relation to said fixed contacts, a thermally responsive latch in electrical series with said movable contacts and engageable with said abutment ledge to hold the said contacts in closed position and spring guide means in sliding engagement with said guide surface, and spring means connected between said support structure and said casing to constantly urge said movable contacts to open position, said spring means being tensioned when said support structure is moved to engage said latch with said abutment ledge and close said contacts.

2. An electric switch as claimed in claim 1, comprising insulator means electrically insulating said guide means from said latch.

3. An electric switch with overload protection comprising fixed contacts, movable contacts in opposed relation to said fixed contacts, structure for supporting said movable contacts for movement toward and from said fixed contacts, spring means constantly urging said structure to position to open the said contacts, said structure in cluding a thermally responsive latch element in electrical series with said movable contacts and including also spring guide mean-s in opposed relation to said latch element, and a fixed guide structure on which said first structure is supported for movement toward and from said fixed contacts, said fixed guide structure including an abutment ledge and defining a guide surface, said latch being releasably engageable with said abutment ledge and said spring guide means being in sliding engagement with said guide surface.

4. In an electric switch having overload protection, a fixed contact, a movable contact, spring means continuously acting to separate said contacts, a thermal latch deflected by overload and arranged in series with said contacts and associated with said movable contact to move therewith as a unit, said unit carrying spring guide means in opposed relation to said latch, fixed structure including a shoulder with which said latch normally engages to hold said contacts 15 0 Numb er 5 tion.

RICHARD C INGWERSEN.

References Cited in the file of this patent UNITED STATES PATENTS Name Date 1,704,379 Aichele Mar. 5, 1929 2,187,606 Jackson et a1 Jan. 16, 1940 2,422,508 Von Hoorn June 17, 1947 

